Download The Role of Regulatory T Cells in Rheumatoid

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Medical Research Society
M88
Nephrotoxic nephritis in FcRy chain and Fcy receptor 111
deficent mice.
R.M. Tan?, K.A. Davies‘, M. Botto’, MJ. Walport‘ and H.T.
COOP,
‘Rheumatology Section, Imperial College of Medicine,
Hammersmith Hospital, Du Cane Road, London, W12 ONN,
*Department of Histopathology, Hammersmith Hospital, Du
Cane Road, London, W12 0”.
Fcy receptors bind the Fc portion of IgG, initiating innate
inflammatory responses. In the mouse there are two activatory Fcy
receptors, Fcy receptor 1 (FcyRI), and Fcy receptor 111 (FcyRIII)
which possess a common y chain signalling subunit. Using FcRy
chain deficient mice (FcRy-I-) lacking both activatory receptors I and
111, and Fcy receptor Ill deficient mice (C57BU6 background), we
have investigated the role of these molecules in accelerated
nephrotoxic nephritis. Mice were pre-immunized with 0.2mg of
sheep IgG and given intravenous sheep antimouse glomerular
basement membrane antibody five days later. Compared with wild
type (WT) and FcyRIII-I- mice, FcRy-I- animals were strongly
protected from glomerular thrombosis - 0% vs 71&9% (WT) and
59*9% (FcyRIII-I-) at day 7 post nephrotoxic serum (mean+SEM,
n=9 per group). The FcRy-l- mice were also protected from crescent
formation - 0% vs 27*6% (WT) and 1 6 6 % (FcyRIII-/-), and renal
failure - serum crcatinine 50~3pnoV1(FcRy-l-) vs 152~17pmoVl
(WT) and 112i17pmolll (FcyRIII-/-). These results show that FcRyl- animals are strongly protected from disease (p<0.05 when
compared with WT or FcyRIII-I-) whilst there was no statistically
significant difference between WT and FcyRIII-I- at this dose of
serum. When half the dose of serum was given (5mg/mouse)
FcyRIII-l- mice were mildly protected from crescent formation (WT
25&4% vs FcyRIII-I- 1 7 6 % ) and glomerular thrombosis ( 4 5 6 % vs
27&4%) (p<0.05). These results show that FcyRIII has a role in
disease pathogenesis, but cannot fully explain the marked protection
of FcRy-I- mice from accelerated nephrotoxic nephritis. To examine
the role of Fcy receptors on circulating cells compared with intrinsic
renal cells, wild type bone marrow was transplanted into FcRy-lanimals after total body irradiation. These mice were no longer
protected from accelerated nephrotoxic nephritis, demonstrating that
disease in this model is mediated primarily by Fcy receptors on
circulating leukocytes rather than on intrinsic renal cells.
M89
Evidence of self-HLA restriction in CD4+CD25+ regulatory cells
David S. Game and Robert I. Lechler
CD4+CD25+ T cells have been shown to be important in preventing
autoimmune disease in animal models. In vitro studies using human
blood have shown that CD4+CD25+ T cells are a naturally occurring
population with suppressive properties. There is considerable debate
about how these cells mediate suppression: some groups advocate
release of suppressive cytokines while others favour cell-contact
dependent mechanisms. Furthermore, the specificity of the
CD4+CD25+ regulatory cells is uncertain, in particular are they self
HLA-restricted? Our working hypothesis is that they are specific for
widely expressed self peptides, presented by self HLA class I1
molecules. Having recently demonstrated the ability of CD4+CD25+
cells to inhibit alloresponses against foreign HLA molecules, we
have designed experiments to reveal self HLA restriction by the
CD4+CD25+ regulatory cells. Using HLA-DR7- homozygous
rcsponder cclls, mixed leucocyte reaction cultures were performed
using stimulator cells that expressed either 2, 1, or no HLA-DR
mismatches. Our prediction was that the regulatory cells would be
most efficient in the combinations in which DR7 (the self HLA
restriction element) was expressed by the stimulator cells (i.e. 0 or 1
mismatched). The influence of depleting the responder population of
CD4+CD25+ cells was assessed in these allogeneic combinations.
The amount of proliferation and IL2 secretion after depletion of the
CD4+CD25+ cells divided by that before depletion gives an
indication of the degree of suppression mediated by these cells. We
have reproducibly shown that, indeed, the degree of suppression
follows the trend 2<1<0. A typical set of ratios would be 5.65 for 0
mismatch, 1.65 for 1 MM and 1.14 for 2MM.
These results support the concept that this population of regulatory
cells is indeed self HLA-restricted and have important implications
in the design of strategies to maximise their potential to regulate
unwanted immune responses, such as those against transplanted
tissues and self.
M90
TIIE ROLE OF REGULATORY T CELLS IN RHEUMATOID
ARTHRITIS
CA Lawson, F Ponchel, AW Boylston, P Emery, JD Isaacs.
Molecular Medicine Unit and Department of Rheumatology,
University of Leeds.
There has been much recent interest in a subpopulation of CD4+ T
cells that also express the IL-2 receptor a chain (CD25). These cells
appear to exert regulatory effects and contribute to peripheral
tolerance via a dominant mechanism. In animal models, removal of
this population results in development of autoimmune disorders.
Recently, the presence of these regulatory cells has been documented
in humans. Our preliminary work has demonstrated that there are
two populations of CD4+CD25+ T cells, CD2Sh@’and CD25lW. A
recent publication showed that it is predominantly the CD2Sh@’
subgroup that exhibit strong regulatory properties in v i m (BaecherAllan et al, Journal of Immunology 2001).
Rheumatoid arthritis (RA) is thought to have an autoimmune basis in
view of the presence of circulating autoantibodies, linkage to class I1
MHC, and the increased prevalence of RA in families with other
autoimmune diseases. We are testing the hypothesis that the
regulatory T cell population is abnormal in those who develop RA,
resulting in immune dysregulation and disease development. We
have examined peripheral blood lymphocytes from patients with
early disease (less than 12 months from symptom onset) who have
had no previous immunosuppressive drug therapy. Initial results
suggest that there is no significant difference in the proportion of
CD4+ T cells expressing high levels of CD25 between healthy
controls (mean 4.4%) and early RA (mean 4.1%). We are continuing
to collect data for both of these groups, as well as from those with
RA whose disease is in clinical remission, and a group with selflimiting reactive arthritis.
We are now beginning to investigate potential functional differences
in this regulatory T cell population in RA, looking at proliferative
responses to mitogens and recall antigens, and analysing the
expression of anergy-related genes.